diff --git a/hadoop/2.7.4/Dockerfile b/hadoop/2.7.4/Dockerfile
index bd78419..e26c6a3 100644
--- a/hadoop/2.7.4/Dockerfile
+++ b/hadoop/2.7.4/Dockerfile
@@ -23,10 +23,12 @@ RUN chown root:root /root/.ssh/config
 RUN echo "Port 2122" >> /etc/ssh/sshd_config
 
 # Install Hadoop
-RUN wget -O hadoop.tar.gz https://archive.apache.org/dist/hadoop/common/hadoop-2.7.4/hadoop-2.7.4.tar.gz && \
-tar -xzf hadoop.tar.gz -C /usr/local/ && rm hadoop.tar.gz
+ENV HADOOP_VER 2.7.4
 
-RUN ln -s /usr/local/hadoop-2.7.4 /usr/local/hadoop
+RUN wget -O hadoop.tar.gz https://archive.apache.org/dist/hadoop/common/hadoop-$HADOOP_VER/hadoop-$HADOOP_VER.tar.gz && \
+	tar -xzf hadoop.tar.gz -C /usr/local/ && rm hadoop.tar.gz
+
+RUN ln -s /usr/local/hadoop-$HADOOP_VER /usr/local/hadoop
 
 ENV HADOOP_HOME /usr/local/hadoop
 ENV PATH $PATH:$HADOOP_HOME/bin:$HADOOP_HOME/sbin
diff --git a/hadoop/2.7.4/README.md b/hadoop/2.7.4/README.md
index 89ef602..17f7b37 100644
--- a/hadoop/2.7.4/README.md
+++ b/hadoop/2.7.4/README.md
@@ -1,85 +1,115 @@
-# based on alpine
+# Deploy one Hadoop Cluster with docker
 
-## Create a hadoop cluster in swarm mode
-
-`--hostname` needs docker 1.13 or higher
+## Start Master
 
 ```bash
 docker service create \
---name hadoop-master \
---hostname hadoop-master \
---network swarm-net \
---replicas 1 \
---endpoint-mode dnsrr \
-newnius/hadoop
+  --name hadoop-master \
+  --hostname hadoop-master \
+  --network swarm-net \
+  --replicas 1 \
+  --detach=true \
+  --endpoint-mode dnsrr \
+  --mount type=bind,source=/etc/localtime,target=/etc/localtime \
+  newnius/hadoop:2.7.4
+```
+
+## Start slaves
+
+```bash
+docker service create \
+  --name hadoop-slave1 \
+  --hostname hadoop-slave1 \
+  --network swarm-net \
+  --replicas 1 \
+  --detach=true \
+  --endpoint-mode dnsrr \
+  --mount type=bind,source=/etc/localtime,target=/etc/localtime \
+  newnius/hadoop:2.7.4
 ```
 
 ```bash
 docker service create \
---name hadoop-slave1 \
---hostname hadoop-slave1 \
---network swarm-net \
---replicas 1 \
---endpoint-mode dnsrr \
-newnius/hadoop
+  --name hadoop-slave2 \
+  --network swarm-net \
+  --hostname hadoop-slave2 \
+  --replicas 1 \
+  --detach=true \
+  --endpoint-mode dnsrr \
+  --mount type=bind,source=/etc/localtime,target=/etc/localtime \
+  newnius/hadoop:2.7.4
 ```
 
 ```bash
 docker service create \
---name hadoop-slave2 \
---hostname hadoop-slave2 \
---network swarm-net \
---replicas 1 \
---endpoint-mode dnsrr \
-newnius/hadoop
+  --name hadoop-slave3 \
+  --hostname hadoop-slave3 \
+  --network swarm-net \
+  --replicas 1 \
+  --detach=true \
+  --endpoint-mode dnsrr \
+  --mount type=bind,source=/etc/localtime,target=/etc/localtime \
+  newnius/hadoop:2.7.4
 ```
 
+## Init for the first time
+
+#### format dfs first
+Run these commands on the master node.
+
 ```bash
-docker service create \
---name hadoop-slave3 \
---hostname hadoop-slave3 \
---network swarm-net \
---replicas 1 \
---endpoint-mode dnsrr \
-newnius/hadoop
-```
-
-## Init && Test
-
-In the first deploy, format dfs first
-
-### stop cluster (in master)
-```bash
+# stop HDFS services
 sbin/stop-dfs.sh
-```
 
-### format hdfs (in master)
-```bash
+# format HDFS meta data
 bin/hadoop namenode -format
-```
 
-### start cluster (in master)
-```bash
+# restart HDFS services
 sbin/start-dfs.sh
 ```
 
-### Run a test job
+## Run a test job
+To make sure youui have successfully setup the Hadoop cluster, just run the floowing commands to see if it is executed well.
 
 ```bash
 # prepare input data
 bin/hadoop dfs -mkdir -p /user/root/input
 
+# copy files to input path
 bin/hadoop dfs -put etc/hadoop/* /user/root/input
-```
-```bash
+
+# submit the job
 bin/hadoop jar share/hadoop/mapreduce/hadoop-mapreduce-examples-2.7.4.jar grep input output 'dfs[a-z.]+'
-
 ```
 
-### monitor cluster in browser
+## Browse the web UI
+You can expose the ports in the script, but I'd rather not since the slaves shoule occupy the same ports.
 
-YARN: hadoop-master:8088
+To access the web UI, deploy another (socks5) proxy to route the traffic.
 
-HDFS: hadoop-master:50070
+If you don't one, try [newnius/docker-proxy](https://hub.docker.com/r/newnius/docker-proxy/), it is rather easy to use.
 
-_Proxy needed: newnius/docker-proxy_
+Visit [hadoop-master:8088](hadoop-master:8088) fo YARN pages.
+
+Visit [hadoop-master:50070](hadoop-master:50070) fo YARN pages.
+
+## Custom configuration
+
+To persist data or modify the conf files, refer to the following script.
+
+The `/config/hadoop` path is where new conf files to be replaces, you don't have to put all the files.
+
+```bash
+docker service create \
+  --name hadoop-master \
+  --hostname hadoop-master \
+  --network swarm-net \
+  --replicas 1 \
+  --detach=true \
+  --endpoint-mode dnsrr \
+  --mount type=bind,source=/etc/localtime,target=/etc/localtime \
+  --mount type=bind,source=/data/hadoop/config,target=/config/hadoop \
+  --mount type=bind,source=/data/hadoop/hdfs/master,target=/tmp/hadoop-root \
+  --mount type=bind,source=/data/hadoop/logs/master,target=/usr/local/hadoop/logs \
+  newnius/hadoop:2.7.4
+```
diff --git a/hadoop/2.7.4/bootstrap.sh b/hadoop/2.7.4/bootstrap.sh
index 42f4f75..4289858 100755
--- a/hadoop/2.7.4/bootstrap.sh
+++ b/hadoop/2.7.4/bootstrap.sh
@@ -9,8 +9,12 @@ rm /tmp/*.pid
 # installing libraries if any - (resource urls added comma separated to the ACP system variable)
 cd $HADOOP_PREFIX/share/hadoop/common ; for cp in ${ACP//,/ }; do  echo == $cp; curl -LO $cp ; done; cd -
 
-# replace config
-cp /mnt/hadoop-config/* $HADOOP_PREFIX/etc/hadoop/
+## replace config
+: ${EXTRA_CONF_DIR:=/config/hadoop}
+
+if [ -d "$EXTRA_CONF_DIR" ]; then
+	cp $EXTRA_CONF_DIR/* $HADOOP_PREFIX/etc/hadoop/
+fi
 
 /usr/sbin/sshd